Heat exchanger



May 27, 1969 w. BQTTUM HEAT EXCHANGER Filed March 10, 1967 EMWEMQEQQINVENTOR.

I EDWARD W. BOTTUM.

WILSON, SETTL E BATCHELDER Al ATT'YS. CR 6 United States Patent3,446,032 HEAT EXCHANGER Edward W. Bottum, 9357 Spencer Road, Brighton,Mich. 48110 Filed Mar. 10, 1967, Ser. No. 622,132 Int. Cl. F28f N06, N36

U.S. Cl. 62-513 1 Claim ABSTRACT OF THE DISCLOSURE The present inventionrelates to a heat exchanger for a refrigeration system, and moreparticularly to a heat exchanger for the exchange of heat between arelatively cold fluid and a relatively warm fluid, the heat exchangeremploying improved means for placing the fluids in heat exchangerelationship.

Background of the invention Heat exchangers are employed inrefrigeration systems for the exchange of heat between fluids, generallythe relatively cold refrigerant gases from the evaporator and relativelywarm liquid refrigerant from the condenser. The refrigerant gas which isexhausted from the evaporator of the refrigeration system is relativelycold. The liquid refrigerant which is drawn from the condenser of arefrigeration system is relatively warm. In order to improve theefliciency of the refrigeration system, it is desirable to heat exchangethe warm liquid with the cold gas. The heat exchanger of the presentinvention provides an improved means for efliciently effectuating thedesired heat exchange. Other fluids are, however, also heat exchanged.For example, cold evaporator gas may be heat exchanged with warmcompressor gas.

It is therefore an object of the present invention to provide animproved heat exchanger for a refrigeration system.

Another object of the invention is to provide a heat exchanger whereinthe liquid refrigerant is caused to follow a helical path around anelement through which the refrigerant gas passes, the helical pathcausing the liquid to have good contact with said element and alsoincreasing the velocity of the liquid, both of which result in improvedheat transfer.

A further object of the invention is to provide an element for thepassage of refrigerant gas therethrough and refrigerant liquidthereover, the element having longitudinally extending flutes in thewall thereof to increase the heat transfer surface and also to improvethe wiping action of the refrigerant as it passes thereover.

An additional object of the invention is to provide, in the elementthrough which the refrigerant gas passes, an internally spiralled memberwhich maintains the refrigerant gas in direct wiping action with theinternal surface of the element.

A further object of the invention is to provide an increased heattransfer surface in the element through which the refrigerant gaspasses.

Other objects of this invention will appear in the following descriptionand appended claim, reference being had to the accompanying drawingforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

In the drawing:

FIGURE 1 is a view in perspective of the heat exchanger of the presentinvention with a portion of the external casing broken away for thepurpose of clarity and schematically illustrating the heat exchangerconnected in a refrigeration system; and

FIGURE 2 is a view of the element within the heat exchanger throughwhich the refrigerant gas passes with parts broken away for the purposeof clarity.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawing, since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Alsoit is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

Refering to FIGURES 1 and 2, it will be noted that the heat exchanger 10comprises an outer elongated tubular casing member 12 and an innerelongated casing member 14. The inner casing member 14 is fabrricated ofa material having high thermal conductivity properties.

The outer casing 12 has an inlet 16 and an outlet 18. The inlet 16 isconnected to, for example, the condenser of a refrigeration system whilethe outlet 18 is connected to, for example, the evaporator of arefrigeration system. Warm liquid refrigerant is drawn from thecondenser and passes into the heat exchanger 10 via the inlet 16. Theliquid refrigerant then passes over the outer surface of the innercasing 14 and exits from the heat exchanger via the outlet 18.

The inner casing 14 has a central portion 20 of reduced diameter. Theportion 20 is spaced from the interior surfaces of the outer casing 12to define a passageway for the flow of liquid refrigerant through theexchanger. The ends 22, 24 of casing 14 are enlarged and contact theinterior surface of casing 12. The juncture thereof is sealed as bybrazing or soldering. An inlet fitting 26 and an outlet fitting 28extend from the casting 14. The juncture of the fittings 26, 28 with thecasing 14 are sealed as by soldering or brazing.

It will be noted that the casing 14 has longitudinally extending flutes30 spaced around the entire periphery thereof. The flutes 30 serve adual purpose. Firstly, fluting of the casing 14 results in a largersurface area available for heat transfer. This is true both with respectto the liquid refrigerant which flows across the exterior surface andthe refrigerant gas which flows across the interior surface. The flutesalso provide a better wiping action of the fluids on the heat transfersurface. This improves the heat transfer coeflicient.

A helically wound coil 32 is provided on the reduced diameter portion 20of the casing 14. The coil 32 defines, along with the casing surfaces, ahelical passageway for flow of the liquid refrigerant. This results indirecting the flow of liquid refrigerant as close to the fluted surfaceof casing 14 as possible and improves the wiping action of the liquid asit passes thereover. The liquid is forced to sweep the surface of casing14 and cannot form into separate flow pockets or strata. The stratumclosest to casing 14, in elfect, acts as an insulator and therebydecreases the heat transfer rate. Such strata may form if the liquidflows longitudinally across the surface of element 14 rather thanhelically therearound. An additional advantage in use of the coil 32 isthat the passageway formed by the coil acts as a restriction to the flowof liquid. Restricting the flow results in increasing the velocity offlow. An increase in velocity is advantageous because improved heatexchange is achieved at higher velocities.

Referring to FIGURE 2, it will be noted that a spiral metallic strip 34is provided within casing 14. The edges 36 of the strip 34 are incontact with the internal surfaces of the casing 14. The strip 34extends from end portions 22, 24 across the length of the portion 20.The strip 34 forms a helical passageway for the flow of gas through thecasing 14. This is advantageous in that it maintains the gas in directwiping action with the internal fluted surface of casing 14 in a mannersimilar to the coil 32. This improves the heat transfer between theliquid flowing through casing 12 and the gas flowing through casing 14.Additionally, the spiral strip provides additional heat transfer area.

It will be noted that the strip 34 has transverse corrugations 36. Thecorrugations 36, in addition to providing a larger heat transfersurface, cause turbulence. This turbulence improves the contact betweenthe gas and the heat transfer surfaces to result in increased heattransfer.

In the construction described, the liquid refrigerant enters throughinlet 16 and exits through outlet 18 while the gas enters through inletfitting 26 and exists through outlet fitting 28. This results in acounter-current flow of the gas and liquid. Such a counterflow resultsin the most eflicient heat transfer. However, the gas and liquid mayflow in the same direction if this is desired for installation purposes.

The juncture of the casing 14 with the casing 12 has been disclosed asbeing brazed or soldered. Alternately, the ends of the casing 14 may bespun or swaged to result in a mechanically sound fluid tight connection.In such a construction, there are no internal joints. An end capconstruction may also be used as an alternate to directly mechanicallyconnecting casing members 12 and 14.

The casing 14 may be constructed of a material which is not easilycorroded, such as copper. However, in view of the fact that casing 14 isentirely contained within casing 12, it may be fabricated of a materialsuch as steel because it will not be subjected to corrosion or rustingcaused by moisture or other materials in the ambient atmosphere.

FIGURE 1 illustrates the heat exchanger schematically connected into arefrigeration system. The inlet 28 of the heat exchanger 10 is connectedto the outlet of an evaporator 38 via line 40. Cold refrigerant gas isthus injected into one end of the heat exchanger. The outlet 26 of theinner casing member 14 is connected to the inlet of compressor 42 vialine 44. The outlet of the compressor 42 is connected to the inlet of acondenser 46 via line 48. The outlet of the condenser 46 is connected tothe inlet 18 of the outer casing 12 via line 50. The outlet 16 of theouter casing 12 is connected to the inlet of the evaporator 38 via line52.

It will be noted in the above-described system that the connections 16,18, of the outer casing 12 are incorporated into the refrigerationsystem in a manner causing warm refrigerant liquid from the condenser 46to flow from left to right as viewed in FIGURE 1, while the connections26, 28 of the inner casing member 14 are incorporated into therefrigeration system to cause the cold refrigerant gas from theevaporator to flow from right to left as viewed in FIGURE 1, thusresulting in the desired countercurrent flow which results in maximumheat exchange.

Having thus described my invention, I claim:

1. In a refrigeration system including a condenser, a compressor, anevaporator and a heat exchanger, said heat exchanger functioning tocause heat exchange between the relatively cold gases from theevaporator and the relatively warm liquid from the compressor, said heatexchanger comprising an outer casing member, an inner casing memberpositioned therein, said inner casing member being fabricated fromthermally conductive material, the inner casing member being spaced fromthe interior surface of the outer casing member, said inner casingmember being fluted in the direction of fluid flow to provide both aninterior and an exterior fluted surface to increase the heat transfersurface thereof and to assist in maintaining turbulent flow of fluid, ahelically spiralled strip member Within said inner casing member todefine, with the inner surface of said inner casing member, a helicalpath for the flow of fluid through said inner casing member, said stripmember being transversely corrugated, a helical coil provided on theexterior surface of said inner casing member to define a helicalpassageway for the flow of fluid through said outer casing member, eachof said casing members having an inlet and an outlet, the inlet of theouter casing member being connected to the outlet of the condenser, theoutlet of the outer casing member being connected to the inlet of theevaporator, the inlet of the inner casing member being connected to theoutlet of the evaporator and the outlet of the inner casing member beingconnected to the compressor.

References Cited UNITED STATES PATENTS 2,120,754 6/1938 Newton -1543,177,936 4/ 1965 Walter 165-109 X FOREIGN PATENTS 481,806 10/ 1916France. 1,208,314 1/ 1966 Germany.

ROBERT A. OLEARY, Primary Examiner.

A. W. DAVIS, Assistant Examiner.

US. Cl. X.R.

